The use of enzymes to effect specific chemical transformations is well known. In carrying out such transformations, cell-free preparations are commonly employed in batch-type processes. The rather costly procedures normally used in the production of cell-free enzyme preparations raises questions of economic feasibility in view of the fact that the enzymes are used one time only in batch-type operations. It is this fact which has prompted an increased interest in the preparation of various forms of immobilized enzymes which would permit repeated use of the enzymes thus making such processes commercially attractive.
A number of immobilizing agents for enzymes have been investigated but a totally satisfactory process which is generally applicable to a large number of enzymes has not yet been found. Various problems such as enzyme inactivation resulting from the immobilization procedure, low substrate flow rates through the immobilized enzyme and difficulty in purifying enzymes prior to immobilization have prevented wide commercial use of continuous-type processes based on immobilized enzymes. The present invention provides a simple, convenient and effective means of adapting enzymes for use in either continuous or batch-type operations which largely overcomes the foregoing limitations. It has been found that cell-free enzyme preparations can be easily converted to stable enzyme-containing aggregates through the use of polyelectrolyte flocculating materials. The process disclosed herein does not require enzyme purification, enzyme inactivation is minimal and the immobilized enzyme material prepared in the presence of an inert support material is characterized by a loose, noncompacting mass which allows relatively high flow rates of substrate solution through the enzyme reactor bed. Moreover, this immobilization procedure can be adapted to a wide variety of enzymes and enzymatic processes, enzymes from plant or animal sources being equally amenable to the disclosed procedure.